The Instagram Ruby Gem (adapted poorly but workingly by innonate - not the official gem!)

gem install instagram-innonate

require "sinatra"
require "instagram"

enable :sessions

CALLBACK_URL = "http://localhost:4567/oauth/callback"

Instagram.configure do |config|
  config.client_id = "YOUR_CLIENT_ID"
  config.client_secret = "YOUR_CLIENT_SECRET"
end

get "/" do
  '<a href="/oauth/connect">Connect with Instagram</a>'
end

get "/oauth/connect" do
  redirect Instagram.authorize_url(:redirect_uri => CALLBACK_URL)
end

get "/oauth/callback" do
  response = Instagram.get_access_token(params[:code], :redirect_uri => CALLBACK_URL)
  session[:access_token] = response.access_token
  redirect "/feed"
end

get "/feed" do
  client = Instagram.client(:access_token => session[:access_token])
  user = client.user

  html = "<h1>#{user.username}'s recent photos</h1>"
  for media_item in client.user_recent_media
    html << "<img src='#{media_item.images.thumbnail.url}'>"
  end
  html
end

require "rubygems"
require "instagram"

# Get a list of a user's most recent media
puts Instagram.user_recent_media(777)

# Get the currently authenticated user's media feed
puts Instagram.user_media_feed

# Get a list of recent media at a given location, in this case, the Instagram office
puts Instagram.location_recent_media(514276)

# All methods require authentication (either by client ID or access token).
# To get your Instagram OAuth credentials, register an app at http://instagr.am/oauth/client/register/
Instagram.configure do |config|
  config.client_id = YOUR_CLIENT_KEY
  config.access_token = YOUR_ACCESS_TOKEN
end

# Get a list of all the users you're following
puts Instagram.follows

# Get a list of media close to a given latitude and longitude
puts Instagram.media_search("37.7808851,-122.3948632")

# Get a list of the overall most popular media items
puts Instagram.media_popular

# Search for users on instagram, by name or username
puts Instagram.user_search("shayne sweeney")